The Load Theory of attention and cognitive control (e.g. Lavie et al, 2004) proposes a dissociation between limited capacities for perception and working memory control. Previous support rested on experimental demonstrations of opposite effects of perceptual load and working memory load on distractor perception (Lavie, 2005 for review). Here we apply an individual differences approach to both task performance and brain structure, dissociating perceptual capacity from working memory capacity across different attention-demanding tasks. Task performance measures in change detection, multiple object tracking (MOT), subitizing (the ability to detect small numbers of items in parallel from a rapid presentation) and three complex span working memory tasks were assessed for 112 participants. Factor analyses supported a two-factor model in which distinct sources of common variance were found in change detection, MOT and subitizing in one factor and working memory performance in another. Structural MRI scans were obtained for 44 participants from this sample. Voxel-Based Morphometry (VBM) analysis indicated a common region of grey matter density in the right Temporo-Parietal Junction (rTPJ) associated with perceptual capacity: higher grey matter density in rTPJ was found for individuals with higher perceptual capacity across change detection, MOT and subitizing. In contrast; higher working memory capacity was associated with greater grey matter density in the left middle frontal gyrus. Furthermore, the correlates of perceptual capacity remained significant when controlling for variance accounted for by working memory capacity, and vice versa. These results provide a new line of support for the Load Theory proposal of dissociable perceptual and working memory control capacities. The association of these functions with differences in the grey matter density of parietal and frontal cortex respectively suggests that they represent a lasting individual attribute.